If you don’t want to take any chances with your data, it is recommended that you backup hard disk partition table. Last Friday I was discussing some issues with one of our customer and he pointed out me dd command.

Backup MBR with dd command

dd the old good command which now backup partition tables even writes CDs ;). Backing up partition is nothing but actually backing up MBR (master boot record). The command is as follows for backing up MBR stored on /dev/sdX or /dev/hdX :# dd if=/dev/sdX of=/tmp/sda-mbr.bin bs=512 count=1

Replace X with actual device name such as /dev/sda.

Now to restore partition table to disk, all you need to do is use dd command:# dd if= sda-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446

dd command works with Solaris, HP-UX and all other UNIX like operating systems. Read man page of dd for more info.

If you are using hot swappable hard disk and created new partition using fdisk then you need to reboot Linux based system to get partition recognized. Without reboot you will NOT able to create filesystem on your newly created or modified partitions with the mke2fs command.

However with partprobe command you should able to create a new file system without rebooting the box. It is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table.